Tesla CEO Elon Musk added $9.7 billion to his net worth on Monday, positioning him behind only Amazon CEO Jeff Bezos in the race to be the richest man in the world, according to the Bloomberg Billionaires Index.

Musk is worth $155 billion compared to Bezos’ $185 billion, according to Bloomberg.

Forbes calculates Musk’s net worth to be slightly lower at $143.1 billion, putting him behind LVMH’s Bernard Arnault and family, who are valued at $143.5 billion.

Musk’s net worth has ballooned this year, allowing him to rocket past fellow billionaires, including Facebook founder Mark Zuckerberg.

Musk’s net worth has grown on the strength of Tesla and SpaceX.

The market value of the electric vehicle maker Tesla reached $608 billion on Monday for the first time and is now just one of five S&P 500 companies to join the exclusive club as tracked by Dow Jones Market Group.

The company is set to be added to the index, which is the broadest measure of the stock market, on Dec. 21, and since the inclusion was announced last month investors have pushed the stock to record highs of $641.76 per share growing the market cap by $221.49 billion.